Stereoselective synthesis of acyclic chiral amines by [alpha]-amidoalkylation /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | A method for the preparation of chiral N-acyl-N,OMe-acetals 38-44 has been developed. Seven N-acyl-N,OMe-acetals which possess different groups on the side chain were prepared by decarboxylation/methoxylation from chiral carbamates of α-amino acids in 65% to 93% yield. These reagents were used as stable precursors of N-acyliminium ions in the investigation of α-amidoalkylation reactions with five nucleophiles. Reactions of N-acyl-N,O-acetals 38-44 with 4-methoxyphenol (58) and EtAlCl2 gave ortho specific benzylamines 61-67 with 53% to 96% yield and 64% to 91% diastereomeric excess (de) depending on the structure of the side chain (R1). But for other aromatic compounds, most of starting materials decomposed to carbamate 45 with zero to very low yield of desired products. Reactions of N-acyl-N,O-acetals 38-44 with allyltrimethylsilane (70) and BF3*Et2O were very smooth. They gave homoallylamines 72-78 with 85% to 99% yield and 33% to 95% de depending on the structure of R1. Reactions of N-acyl-N,O-acetals 38-44 with 1-phenyl-1-(trimethylsilyloxy)-ethylene (80) and BF3*Et2O gave β-amino ketones 82-88 with 80% to 98% yield and 10% to 70% de. Reactions of N-acyl-N,O-acetals 38-44 with silyl ketene acetal 89 and BF3*Et2O and subsequent desilylation gave β-amino esters 91-97 with 60% to 99% yield and 10% to 95% de depending on the structure of R1. Reactions of N-acyl-N,O-acetals 38-44 with trimethylsilyl cyanide (99) and BF3*Et2O gave α-amino nitriles 101-107 with 65% to 95% yield and 5% to 72% de. The molar ratio of 1:1 TMSCN/BF3*Et2O might be the optimum condition to reduce decomposition of starting material and to increase yield. Decomposition of N-acyl-N,O-acetals 38-44 to carbamate 45 was the most serious side reaction. This decomposition can be suppressed or decreased to a minimum amount by using Method A or B depending on the nucleophilic reagents... |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xii, 145 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |